The SMTP server requires a secure connection or the client was not authenticated

Question

I am getting this error

The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Must issue a STARTTLS command first. e17sm974159fak.34

Web.config

<mailSettings> <smtp deliveryMethod="Network" from="[email protected]"> <network defaultCredentials="false" host="smtp.gmail.com" port="587" userName="[email protected]" password="12345678" /> </smtp> </mailSettings>

Code file

public void Submit() { EnsureCurrentlyValid(); // Send via email var message = new StringBuilder(); message.AppendFormat("Date: {0:yyyy-MM-dd hh:mm}\n", DateTime.Now); message.AppendFormat("Email from: {0}\n", Name); message.AppendFormat("Email: {0}\n", Email); message.AppendFormat("Message: {0}\n", Message); SmtpClient smtpClient = new SmtpClient(); MailMessage m = new MailMessage( "[email protected]", // From "[email protected]", // To "Suggestion/Comments", // Subject message.ToString()); // Body smtpClient.Send(m); }

Hello @coure2011 , If you get the solution of your problem then please help me, because I am getting the same error. — Abhishek
– Abhishek, Commented Jul 23, 2016 at 6:35

Darin Dimitrov · Accepted Answer · 2010-12-20 18:14:05Z

50

Try setting the EnableSsl property to true:

smtpClient.EnableSsl = true;

AFAIK this property can only be set in code and cannot be specified in the config file.

answered Dec 20, 2010 at 18:14

Darin Dimitrov

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1 Comment

Paul Wheeler Over a year ago

See also: stackoverflow.com/questions/32260/…

quentin-starin · Accepted Answer · 2012-01-18 15:42:58Z

Actually you can handle this in your web.config file by adding enableSsl="true". This worked for me and I didn't need to do anything in code.

e.g.

<network host="smtp.gmail.com" enableSsl="true" ... />

Samyuktha Akula · Accepted Answer · 2019-01-11 16:54:59Z

This worked for me:

Need to turn on "Access for less secure apps" on google account(From Email).
Set smtpclient.UseDefaultCredentials = false;

Set smtpclient.EnableSsl = true;

 MailMessage mail = new MailMessage("FromEmail_Address", "ToEmail_Address"); SmtpClient smtpclient = new SmtpClient(); smtpclient.Port = 587; smtpclient.DeliveryMethod = SmtpDeliveryMethod.Network; smtpclient.UseDefaultCredentials = false; smtpclient.Host = "smtp.gmail.com"; smtpclient.UseDefaultCredentials = false; mail.Subject = "Email Subject"; mail.Body = "Content of the email"; smtpclient.EnableSsl = true; smtpclient.Credentials = new System.Net.NetworkCredential() { UserName = "FromEmail_Address", Password = "password of the email" }; client.Send(mail);

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